JAKARTA, Indonesia — The discovery of three dead Javan rhinos has intensified efforts to save one of the world's most endangered mammals from extinction, with an electric fence being built Monday around a new sanctuary and breeding ground.

With only about 50 of the species left in the wild — all but a handful living in one national park in western Indonesia — conservationists are even talking about taking the rare step of relocating some of the 5-ton animals to spread out the population and give the Javan rhino a better chance to survive.

Drought and proximity to an active volcano in the densely forested Ujung Kulon park have raised fears that a natural disaster could destroy almost the entire population at once. In Vietnam, the only other place the rhinos can be found, there are just four.

"Essentially, the eggs are all in one basket," said Dr. Susie Ellis, the executive director of the U.S.-based International Rhino Foundation, which has warned that without drastic action, some rhinos could be extinct in the wild within the next decade.

"A second population really needs to be established."

The Javan rhino, once the most widespread of Asian rhinoceroses, is today the most threatened of five species.

The species was nearly wiped out in 1883 when the Krakatau volcano erupted, spawning a 120-foot (40-meter) tsunami that killed 37,000 people when it inundated more than a hundred villages — and Ujung Kulon.

The greatest threat they face today is from poachers, habitat destruction and competition for food with other species, according to conservationists.

Rhino horns have long been a popular ingredient in traditional Chinese medicines, fetching tens of thousands of dollars each.

A prolonged dry season in western Indonesia has drained some water sources for the rhinos, and there is also a shortage of grass and other staple foods.

Conservationists have been alarmed at losing three Javan rhinos recently.

"When you are talking about populations as small as this, even one death is significant," said Adhi Rachmat Haryadi, a WWF-Indonesia official at the Ujung Kulon park. …